Congenital deafness is a relatively common human disorder, occurring, on average, in 1/1,000 newborns. This kind of disability hampers speech acquisition and, there­fore, normal communication and social integration. Muta­tions in the GJB2 gene are responsible for more than a half of all cases of pre-lingual non-syndromic  recessive and dominant deafness in many Caucasian populations. Apart from mutations in the GJB2 gene, the GJB3 gene muta­tions are also associated with inherited hearing loss, but the patients with GJB3 gene mutations have progressive age at onset, ranging from mild-moderate to profound hearing loss.

We have analyzed a total of 58 families (unrelated patients) with recessive or sporadic deafness from Bashkortostan (Russia) and 35 (60%) of them were found to carry the 35delG mutation. Five different GJB2 gene mutations, including three novel mutations, and one novel GJB3 gene mutation were identified.

In order to explore the ancestry of GJB2 mutations in the patients with non-syndromic inherited deafness, we estimated linkage disequilibrium between the 35delG mutation, other GJB2 gene mutations and flanking micro­satellite markers D13S143, D13S292, and D13S175. Haplotype analysis of the markers D13S292, D13S175 and D13S143 in the peri-centromeric region of chromo­some 13 helped to optimize DNA diagnostics of non-syn­dromic deafness in patients from Bashkortostan. The re­sults presented here, can be used for the development of a simple molecular test, which will be of considerable help.

Key words: deafness; haplotype analysis; GJB2 and GJB3 genes; 35delG mutation; polymorphic loci.